The gray cast iron used in the manufacturing of ordinary castings parts has a tolerance in its morphology of graphite veins sized from 5 to 8 (wherein the size is determined by the thickness.times.length in the gray cast iron material morphology). Such veins result in fine flakes in the structure of the material, providing for increased hardness and resistance within the known standards of specification for castings parts of gray cast iron, specially for rotors and brake drums.
The graphite presentation in the material morphology of the gray cast iron within conventional standards allows the occurrence of graphite veins of types "A" and "B" and occasionally of types "D" and "E".
For example, the graphite veins known for their shape in the material morphology of gray cast iron are type "A"--being irregular disorientated; "B", --being rosette; "C"--being irregular uneven; "D"--being disorientated interdendritic and type "E"--being right interdendritic.
To obtain regular or ordinary castings parts, it is not acceptable, except in meaningless proportions, to have the presence of type "C" graphite veins in the morphology of the gray cast iron, as such morphology produces a less resistant gray cast iron due to its brittleness in structure and in its reduced hardness, which is considered to be of a poor quality.
The gray cast iron is used in the manufacturing of general friction castings parts, specially brake rotors, clutch and brake drums. Besides the ordinary constituent components pertinent to gray cast iron, it also presents the necessary constituent components relevant to its composition, such as copper, manganese, chromium and silicon, in a wide variable ranges of concentration, and it can also present sulfur concentration in restrictive variable ranges.